Embarcadero has just created a new "Rad Studio in Action" page about "Developing REST Servers in Delphi XE using DataSnap" of which I'm the author. The page is references also in this EDN article.
I wrote a white paper, a very long tutorial (about 60 pages) About using Delphi XE DataSnap REST support for building Web applications with jQuery on the client side. This white paper is also the starting point for further code I'm writing. The page has also got three 10 minutes videos that I recorded, introducing the key elements of the white paper. Further on, I'll present a webinar scheduled for January 27th and repeated three times during the day for different time zones. You can sign up for the webinar from the page linked above.